I am curious, does anyone know if there's a way to define the timers in the variant.h file such that they can be overridden by the user's code? For instance, I tried setting up the variant.h file like:

#ifndef TIMER_SERIAL  #define TIMER_SERIAL           TIM9#endif

But it seems that the variant.h file gets compiled before anything I do in the Arduino sketch / header, and I see a warning that TIMER_SERIAL is redefined. Is there a way to make this work? Would be quite useful if the TONE, SERVO and SERIAL timers could all be redefined by the user, while still allowing for a variant default.

Well, in this case you could redefine it at the sketch level, using thebuild_opt.h with:
-DTIMER_SERIAL=TIM9

https://github.com/stm32duino/wiki/wiki/Customize-build-options-using-build_opt.h

Well, in this case you could redefine it at the sketch level, using thebuild_opt.h with:
-DTIMER_SERIAL=TIM9

Hmm, it might be worth surrounding each of the timers defined in variant.h with an#ifndef check then, so that they can be overridden in this way if desired. Are you aware of any disadvantages to doing this? If not, I think I'll add a commit doing this for serial/servo/tone timers.

Hmm, it might be worth surrounding each of the timers defined in variant.h with an#ifndef check then, so that they can be overridden in this way if desired. Are you aware of any disadvantages to doing this? If not, I think I'll add a commit doing this for serial/servo/tone timers.

From my point of view there is no issue to add#ifndef.

Thanks@fpistm. I've noticed a bit of weirdness when using SoftwareSerial with certain pins, and have opened an issue about this (#1093). Hope you can take a look when you get the opportunity.

I might hold off on requesting a merge on this until I understand what's happening there, in case it's something I've introduced or can fix in the pin definitions.

All right, I'm satisfied with these changes and am happy for the PR to be merged. I'll move it from draft now and it is yours to review@fpistm!